1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly relates to a semiconductor device including an internal voltage generating circuit that generates an internal voltage by a charge pump operation.
2. Description of Related Art
Some semiconductor devices require a boost potential that is higher than a power source potential supplied from outside and a negative potential that is lower than a ground potential. Such semiconductor devices include therein an internal voltage generating circuit that generates a boost potential and a negative potential (see Japanese Patent Application Laid-open Nos. 2003-298957, 2007-325430, 2009-1771.7, and 2009-116684). A representative example of the internal voltage generating circuit is a charge pump circuit that performs step up or step down of a voltage by pumping using a capacitor. The charge pump circuit performs a boost operation by repeating a charge operation for charging the capacitor and a discharge operation for pumping the charged capacitor.
An internal voltage, which is an output of an internal voltage generating circuit, is used in various circuit blocks included in a semiconductor device. When these circuit blocks are in a standby state, the internal voltage generating circuit is also in a standby state, to save the power consumption. At this time, it is desirable to set the internal voltage generating circuit to a standby state while it is in a state of a charge operation.
However, when the internal voltage generating circuit is maintained in a state of the charge operation, a predetermined voltage is kept being applied to both ends of the capacitor, and this causes a problem of generating a certain degree of power consumption due to a leakage current. Further, because the capacitor used in the internal voltage generating circuit has a considerably large capacitance as compared to a capacitor connected to a signal line, when low power consumption is required, the power consumption due to the leakage current may reach a level that is not negligible.